The rise in sea surface temperatures has impacted marine ecosystems worldwide. In particular, significant damage has been observed across coral reefs due to bleaching, the breakdown of symbiosis between corals and its endosymbiont Symbiodinium. As the frequency of bleaching events continues to increase, so does the necessity to fully understand the mechanism of symbiosis breakdown. However, this can prove difficult due to the variation in response to temperature stress by different host-symbiont combinations. To determine the genetic response of temperature tolerant and intolerant symbionts to high temperature stress, we utilized the upside-down jellyfish Cassiopea xamanchana system. We infected C. xamanchana with two Symbiodinium clade A species: a temperature tolerant (KB8) and a temperature intolerant (EL1), and exposed the host to high temperature (32°C) to determine the changes in gene expression after 12 and 36 hrs. Under a single host context, we can determine how tolerance is conferred by different Symbiodinium types.
